The present disclosures relate to semiconductor device processing, and more particularly, to a decoupled complementary mask patterning transfer method.
Normal two-mask patterning schemes, such as complementary phase shift mask (cPSM), require both phase shift mask and cut mask exposures to occur prior to an etch. However, there are advantages to transferring each of the mask patterns to the substrate separately. These advantages include separate tuning of the exposure conditions for each mask, elimination of flare effects which result in undesirable interactions between exposures, photoresist trimming on anchored features (prior to the cut mask), and inclusion of assist features which might otherwise be impossible due to image coupling effects. Unfortunately, current schemes exacerbate the vertical etch depth differences between the two mask transfers, leading to excessive active pitting at gate, for example.
Accordingly, it would be desirable to provide an improved patterning scheme for overcoming the problems in the art.